His announcement came after a majority of EU member states last week backed the long-negotiated accord, which Poland has strongly opposed in a rare show of cross-party unity.
European Commission head Ursula von der Leyen is scheduled to sign the agreement on behalf of the EU on Saturday in Paraguay.
On January 21, members of the European Parliament are due to vote on whether to refer the agreement to the Court of Justice of the European Union (CJEU).
The outcome is expected to be close, with a small number of votes likely to decide the result, public broadcaster Polish Radio’s IAR news agency reported.
'We have not said our last word'
Agriculture Minister Stefan Krajewski said Poland had exhausted all options to block the agreement at this stage but would continue its efforts.
“We did everything possible to prevent the signing of this deal,” Krajewski told reporters in Berlin. "We were unable to form a blocking minority, but we have not said our last word."
He said that if the European Parliament’s challenge fails, the Polish government will seek to file its own complaint with the EU's top court.
Krajewski also pointed to safeguard clauses in the agreement which he said were recently strengthened to protect Polish farmers and food producers.
Under those provisions, Poland would be able to impose tariffs on agricultural imports from Latin America if import volumes rise and prices fall by 5 percent.
He added that Poland would not allow food imports that contain prohibited pesticides or fail to meet EU safety standards.
"Food that reaches Polish tables must be safe," he said.
France has said it would pursue similar legal steps, Polish state news agency PAP reported.
The EU-Mercosur agreement, involving Argentina, Brazil, Paraguay, Bolivia and Uruguay, aims to reduce tariffs on agricultural products such as beef, poultry, dairy goods and sugar, while giving European companies greater access to South American markets, officials say.
The deal was initially expected to be finalised in December but was delayed until January 17.
(pm/gs)
Source: IAR, PAP